An organic light emitting device (OLED) is usually composed of two electrodes and an organic material layer of one or more layers disposed between the electrodes.
If a voltage is applied between a first electrode and a second electrode in the organic light emitting device having the structure, holes and electrons flow from the first electrode and from the second electrode, respectively, into the organic material layer, the holes and electrons are recombined with each other to form an exciton, and a photon corresponding to an energy difference is emitted while the exciton falls back to the ground state. By this principle, the organic light emitting device generates visible rays, and an information display device or illumination device may be manufactured by using this.
In general, the organic light emitting device may be manufactured by a method of depositing a first electrode on a substrate, depositing an organic material layer of one or more layers thereon, and then depositing a second electrode thereon. Therefore, in order to emit light generated from the organic material layer, an electrode in a direction to which the light is to be emitted needs to be transparent, and when light is to be emitted in the first electrode direction, the first electrode and also the substrate need to be transparent.